Method of making lead alloys



Patented July 4, 1933 UNITED STATES PATENT OFFICE ROBERT 3". SEOEMAKER,OF CHICAGO, ILLINOIS, ASSIGNOR TO B. & T. METALOOMPANY,

OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS METHOD OI MAKING LEADALLOYS Io Drawing.

This invention relates to the production of lead alloys and its objectis to provide certain novel procedures in the compounding of suchalloys, having in view convenience of .operation, low cost ofmanufacture, uniformity and homogeneity of the product and particularlythe provision of a method whereby small quantities of metals, such ascalclum, aluminum, magnesium and the like, whlch are susceptible ofoxidation may be introduced into and dissolved in a molten batchof'calcium, tin, mercury, magnesium and aluminum. The mercury isoptional, where maximum hardness is not required; and for some purposes,potassium and/or lithium may be used for (part or all of the magneslumwith the disa vantage, however, of making the alloy somewhat unstableand subject.

to drossing or corrosion.

The composition of this particular type of alloy, according to thepreferred formula is as follows:

Calcium 0.3% to 1.0%Preferred amount 0 5% Tin 0.5% to 2.0%P1eferredamount 1.0% Mercury 0.1g; to 0.5%Preferred amount 0.25% Magnesium 0.0 to0.1 %Preferred amount 0.07 Aluminum 0.02% to 0.1%Preferred amount 0.05%

Lead to make up 100%.

In the batch, the quantities of the readily oxidizable ingredients,calcium, magnesiumand aluminum, may be somewhat greater than indicated,depending upon the care taken to prevent or limit oxidation incompounding and remelting.

The mercury is optional, but preferred. It is essential if a high degreeof "hardness is required, and it acts cumulatively with the calcium, tinand magnesium, in increasing the hardness of the lead. Calcium, mercury,tin and magnesium all act as hardeners of the lead and can be used in anaggregate amount considerablv greater than the amount of any single oneof them which it is practical to use.

The allo also comprises .aluminum, the function 0 which is to preventthe calcium and magnesium from drossing out while the alloy is beingcompounded and also in relting, for example, in melting up the inots forcasting. The amount used may vary between the limits as above indicatedApplication filed October 24, 1930. Serial No. 491,081.

but apparently only about 0.03% remains in the alloy. The rest iscarried off by the flux or covering which is employed in compounding themetals as will be described. It is preferable to use, however, morealuminum than actually goes into the compound in order to be certainthat a sufficient amount is actually dissolved in the lead.

Alloys containing magnesium and/or lithium and/ or potassium may berepresented by the following table:

Calcium 0.3% to 1.0% Preferable amount 0.5% Tin 0.5% to 2.0% Preferableamount 1.0% Mercury 0.1% to 0.5% Preferable amount 0.25% Aluminum 0.02%to 0.05%-Preferab1e amount 0.03%

. Magnesium" 0.05% to 0.1% -Preterab1e amount 0.075% Lithium 0.02% to0.06%-Preferable amount 0.04% Potassium 0.02% to 0.06%'Preferable amount0.04%

Lead to make up 100%.

The addition of the lithium and potassium increases the hardness of thealloy where hardness is a desideratum, but at the cost of increasedcorrosibility.

The hardness of the alloy may vary from 18 to 26 Brinell. It may beraised to 28 Brinell by increase of the calcium, but in this .case thedanger of corrosion and drossing is somewhat increased.

The alloy, as above described, or other hardened or toughened leadcompound containing easily oxidizable metals, may be made by one of thetwo following methods:

7 First method.The lead is melted and covered with calcium chloride andthe temperature raised to approximately 1600 Fahronheit, to insure themelting of the calcium chloride, which may form a layer of an inch inthickness on the lead. The metals to be compounded with the lead andwhich are of a readily oxidizable character are introduced into themolten lead through the calcium chloride flux or covering stratum. Thetinand aluminum may be so introduced either as separate metals or,(which is preferable as a matter of convenience), the aluminum and thetin, in whole or part, may be introduced as tin-aluminum .alloy. Thebatch is stirred until the aluminum is completely dissolved in the lead,or so much dissolved as can be held in solution in the lead. Themagnesium is next introduced into the batch in the same manner andthereafter the calcium, as metallic calcium. The calcium is introducedinto the lead' after the other ingredients above named, in order toprevent foaming of the calcium chloride covering, which is like- 1y tooccur if the calcium is put in first or if all of the before mentionedingredients are introduced into the lead at the same time. The lead isnow allowed to cool down to a temperature of about 600 to 700 F. thecalcium chloride covering stripped off, at

' about 1000 F., and themercury added, preferably as a mercury tinalloy. Alternatively the crucible may be removed from the furnace andallowed to cool to dull red heat, approximately 1200 to 1300 F. and themercury tin alloy introduced through the flux. This causes a slight lossof mercury but tends to give a better pouring metal. If lithium and/orpotassium are used, they are introduced into the melt with the mercury,that is while the batch is at a relatively low temperature, and rosin isadded, which by burning creates fumes which keep the air from coming incontact with the metal.

The supernatant calcium chloride stratum on the lead batch serves tokeep the air from contact with the molten metal and thereby prevents ormaterially lessens oxidation of the lead and other metals. Any metalsusceptible to oxidation is likely to be covered with a film of oxide.In passing the pieces of tinaluminum alloy, magnesium and calciumthrough the calcium chloride stratum, the oxide films on these metalsare dissolved by the calcium chloride- The lead will also be,ordinarily, superficially oxidized and in the melting of the lead theoxide will rise to the top of the batch and be dissolved andretained bythe calcium chloride stratum. It is only possible to dissolve metals ofthe t e ind1- cated in the lead if such metals are ree from oxide andthe lead itself is. free from oxide. The batch must be stirred and ifthe calcium chloride were not present to absorb floating oxides of themetals, these oxides would be stirred into the body of the lead. Thestratum of molten calcium chloride serves the triple function ofcleansing the metals introduced into the lead, absorbing oxide from thelead itself and protecting the melt from oxidation by contact with theair.

Secmid method-The lead is melted and covered with a calcium chloridecovering, as described in connection with the first method. The tin andaluminum, preferably as aluminum-tin alloy and metallic magnesium areintroduced into the lead through the flux, as in the first method. Thecalcium is next introduced, not as metallic calcium, but as calcium-leadalloy. The amount of calcium in this case may be slightly less than whenmetallic calcium is used. The crucible is taken from the furnace and themelt allowed to cool to 600 to 700 F., the flux being stripped off. Themercury is then added as mercury-tin alloy; or one may introduce thisingredient to the flux as in the first method.

One advantage of using calcium-lead alloy instead of metallic calcium isthat the alloy is .cheaper. It also contains less impurities into themolten than metallic calcium. Moreover, for a hear ing metal compound,the alloy will be slightly harder, stronger and in machining will cutmore smoothly than when metallic calcium is used. There are fewerdefects, such as laps, porous spots and shrinkages.

Except for the matter of expense, it is possible to use another halogensalt of calcium,

calcium bromide or calcium iodide in place of calcium chloride for theflux stratum.

This application is a continuation in part of my copending applicationSerial No. 297,- 119, filed Aug. 2, 1928, for Bearing metal.

I claim:

1. Method of compounding a lead alloy which consists in melting the leadunder a. molten covering; introducing the tin, aluminum and magnesiuminto the lead through said covering and thereafter the calcium; andintroducing the mercury, lithium, or potassium into the metallic bodywhile it is at a temperature not substantially in excess of 700 degreesFahrenheit.

2. Method of compounding a lead alloy which comprises: melting the leadand holding the same at a temperature of approxi mately ,1600 degreesFahrenheit under 2. molten covering of calcium chloride; introduc ingthe tin, aluminum and magnesium into the lead under said covering andthereafter the calcium; allowing the melt to come down to a temperatureof approximately 600 degrees to 700 degrees Fahrenheit and introducingthe mercury, lithium and potassium body at approximately thistemperature.

3. Method of compounding a lead allo which comprises: melting the leadand hol ing the same at a temperature of approximately 1600 de reesFahrenheit under a moltencovering 0 calcium chloride; introducing thetin, aluminum, and magnesium into the lead under said covering andthereafter the calcium; introducing rosin into the lead when the latteris at a temperature of about 600 to 700 degrees Fahrenheit, and whilethe rosin is burning introducing lithium or potassium into the moltenbody.

4. Method of making a lead alloy containing aluminum, magnesium andcalcium in which the lead in the molten state is covered by a stratumvof calcium chloride and the aluminum and magnesium first introducedinto the lead and thereafter the calcium, all through said calciumchloride stratum.

5. Method of compounding a hardened lead alloy which comprises meltingthe lead under a covering of calcium chloride, introducing tin,aluminum, magnesium and calcium into the lead through the calciumchloride covering, reducin the temperature of the melt and introduclngmercury into the

